Intro to coasts and wave types and tides

The point where the land meets the sea. It is constantly changing due to the effect of land, marine and air processes.

Coasts are regarded as a system because they have inputs of energy which drive key processes which result in outputs.

These inputs lead to erosion depositions and transportation which result in outputs such as 

beaches, sandunes,bars, headlands and bays , cliffs , wave-cut notch,  wave-cut platforms , caves , arches , stacks , stumps.

Marine inputs
waves
saltspray
tides

Atmospheric inputs-
wind speed direction
precipitation
air pressure 
sun

Human in puts
pollution
settlements
defenses

How are waves created- by the wind blowing over the surface of the sea, the friction between the wind and the waves gives waves a circular motion.

Key terms-
Crest is the highest point of the wave
trough is the lowest point
wave frequency is th number of waves per minute
wave period is the tie taken for a wave to travel to one wave length
wave energy- LH2 L- length and H is the height
wave steepness- The ratio of wave height to wave length cannot be steeper that 1:7 as this is when the wave breaks.

Why do waves break ?
There are 2 types of breaking waves constructive and destructive.

Constructive waves - have a long wave length(100m) and a low height. They have a low frequency of 6-8 per minute.  The are known for depositing material up the beach as the wave breaks the swash loses volume and energy as water percolates through the sand. This gives them a weak backwash which means there is no force to pull sediment off the beach leading to deposition.

Destructive waves- High waves steep waves of high frequency (10-14 per minute). As they approach the beach they steepen and when breaking the plunge down. Creating a  powerful backwash this causes the material to be moved away.

Destructive wave

constructive wave

Wave refraction- As waves approach the coast line, they leave deep water and enter shallow water. This causes the wave to be affected by the friction, drag due to contact with the sea bed so waves slow down. This changes the direction of the waves causes them to become more parallel to the coast.The wave energy concentration is on the headlands causing erosion. The low energy waves diverge in the bays causing deposition if sediment due to slowing down of waves. Wave refraction occurs due to the shape of the coast line.

Wave refraction

What is fetch? Is the maximum distance of the sea the wind has blown over in creating the waves.

Tides are periodic rise and fall in the level of the sea. They are caused by the gravitational pull of the sun and the moon. The moon has greater influence as it is closer to us it pulls water towards it creating high tide this causes a budge on the opposite end of earth. areas between the two bulges have low tide.(neap tide)

A spring tide is when there is greatest distance between high tide and low tide. 2 times a month the sun and the moon are positioned to 90* to each other this gives the lower monthly tidal range eg low tide. Which is the spring tide.

neap and sprig tides

Tidal range is the difference between high and low tide.

Storm Surge- is when spring high tide can produce a high water level than high tide.(1953) North sea is affected by SS and leads too erosional landform formation.

Reasons -
high spring tide 
Low pressure
High winds which increases friction.

Consequences-
Water levels exceeded the mean and was 5.6 meters above.
1836 deaths
Properties damage.